Prior posts here are correct- up to a point.
It is true that "kitchen table dealers" faded away by the hundreds in prior decades.
The internet has brought a huge upsurge of mail order and other sales between people that have never met.
In my experience, ATF is at the very least agreeable to "home dealers".
The first step is to see if your local government will allow you to run a mail order business and grant you a business license. The ATF does require that you be able to get one. They'll also require you to get any/all required state licenses and a sales tax account.
I would STRESS the mail order part when trying for the business license. You could claim no walk-in traffic and NO signs. You might need to claim you will be open by appointment only during your regular business hours.
LOTS of people work from home in this internet age, so many licenses are given for home businesses. Traffic and signs in residential neighborhoods are what the zoning board hates.
You do NOT have to have a storefront.
You do NOT have to be open to retail walk-in traffic.
You DO have to get by the local zoning laws and get the business license. Figure it out.
If you can get the business license, you can get all the other paper IF the local Chief LEO will sign off on it.
The local LEO? You MIGHT need to talk to him. I sent the sheriff a brief letter explaining my intent to deal in collectibles.